In the copending application of West, Ser. No. 97,778 filed Nov. 27, 1979, now U.S. Pat. No. 4,260,780 and entitled "Phenylmethylpolysilane Polymers and Process for their Preparation", description is made of a process for the preparation of such polymers wherein phenylmethyldichlorosilane and dimethyldichlorosilane are reacted in solvent solution in the presence of a reducing catalyst of sodium, potassium or a sodium potassium alloy, and in the ratio of 1 mole phenylmethyldichlorosilane per 3-20 moles dimethyldichlorosilane. The phenylmethylpolysilane polymers that are produced are characterized by thermoplasticity which enables their formation into fibers and by insolubility which prevents their being taken into solution for use in the formation of films, coatings, and the like.